Add test script for DPLL

[William Tu]

* intro

In bug 2053155 "Add DPLL and syncE support" below:
https://bugs.launchpad.net/ubuntu/+source/linux-bluefield/+bug/2053155

It requires using a yaml spec file, dpll.yaml, and a python script, cli.py, to verify the correctness.
ex:
$ sudo ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/dpll.yaml \
--dump device-get

We've found that the script and spec file are missing in current repo (Ubuntu-bluefield-5.15.0-1037.39).

* how to fix
Since the existing Bluefield-5.15 doesn't have the tools/net/ynl directory, the efforts to cherry-pick all individual patches shouldn't be too hard due to no dependencies and most likely no conflict, but there are around 200 patches in tools/net/ynl
$ git log --oneline tools/net/ynl/ | wc -l
     205

and for Documentation/netlink/genetlink.yaml (a dependent file for dpll.yaml)
$ git log --oneline Documentation/netlink/genetlink.yaml | wc -l
      15

So we decided to just create a new patch consisting all the required files, shown below:
  create mode 100644 Documentation/netlink/genetlink.yaml
  create mode 100644 tools/net/ynl/cli.py
  create mode 100644 tools/net/ynl/lib/__init__.py
  create mode 100644 tools/net/ynl/lib/nlspec.py
  create mode 100644 tools/net/ynl/lib/ynl.py

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-bluefield/5.15.0-1039.41 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux-bluefield' to 'verification-done-jammy-linux-bluefield'. If the problem still exists, change the tag 'verification-needed-jammy-linux-bluefield' to 'verification-failed-jammy-linux-bluefield'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!